Traditionally the testing of microelectronics for single event upset (SEU) sensitivity has involved actual exposure to the cosmic ray environment by high altitude flight programs or the simulation of the cosmic ray environment through the use of heavy ion beams produced by accelerators. These simulations are expensive and of limited access, thus alternatives have been sought. This research resulted in the building of a system to measure single event upset cross section versus linear energy transfer by using Cf252 fission fragments in conjunction with thin-film scintillators. The first efforts to use Cf252 for SEU testing involved placing a Cf252 source in an evacuated chamber, bombarding the device under test, and calculating a single upset cross section that presumably was the saturation cross section. Such tests do not adequately address the uncertainties associated with the LET dispersion, and fail to usefully characterize the SEU threshold and saturation cross section of a device because there is no means to provide the SEU cross section versus LET curve. The system developed in this research effort addresses these shortcomings.